Page 1
DATA SHEET No. 138
DATE: January, 1942
SUBJECT:
MODEL 730S "UNIPLEX" CARDIOID CRYSTAL MICROPHONE
GENERAL :
tion or speech. The true uni-directional "cardioid"
characteristic of the "Uniplex" allows highly satis-
factory operation under adverse conditions of background noise and reverberation where a conventional
microphone would be practically useless. (See "A
tic Considerations" for a discussion of directional
characteristics).
The "Uniplex" contains a diaphragm-type element
combined with acoustical networks which cause cancellation or sound pressures for sounds incident from the
rear. The crystal is a Grafoi1 (high capacity) bimorph
unit, triple moisture-sealed to withstand adverse climatic conditions. The microphone has a built-in filter circuit for protection against R.F. burnouts. Case
is pivoted at the rear and may be conveniently pointed
in the direction of the desired sound, or pointed up-
wards for non-directional horizontal plane pickup.
The microphone is provided with an S36A Desk
Stand detachable three-way plug and 7-foot single conductor cable. The same Microphone without a stand is
available under the Model No. 730SH.
APPLICATIONS:
and other applications where clear, intelligible reproduction or speech is or prime importance. The Microphone has a high output permitting its use with moderate gain amplifiers. The wide-range unidirectional
characteristic of the "Uniplex" provides an easy solution to the feedback problem in reverberant locations,
permits best utilization of space in small rooms, and
allows a practically complete exclusion or unwanted
noises.
By pivoting the microphone upwards a 360° non-directional horizontal plane characteristic is obtained
which is useful for group or round-table pickup (See
"Acoustic Considerations" for information on non-directional placement).
INSTALLATION:
stand. For overhead suspension, an A35B Suspension
Adapter may be used. Convenient cable changing is
possible due to the built-in receptacle. A 7-foot
single-conductor cable is furnished with plug attached.
(See catalog for bulk length and special cables
plug attached).
across a load resistance of
though an lnput
be used to decrease the low frequency response
of the Mlcrophone for improvement
good low frequency response
ground should be connected to the
A.
The
or
cable.
nectlng cable wlilbe
put level as given
frequency dlscrlmlnatlon introduced by the cable, regardless of length.
Copyrlght Shure Brothers, 1942
plugs are available. Added lengths of
Total Cable Length
7 Ft. (Standard)
25 Ft.
50 Ft.
75 Ft.
100 Ft.
(Expressed
Model 730S is a uni-directional diaphragm-type crystal microphone designed
especially for high quality reproduc-
COUS
Model 730S is designed especially for
voice transmission and is suitable for
public address, amateur broadcasting.
Model 730S is equipped with the standard 5/8"-27 thread and may be mounted
on any Shure desk., banquet, or, floor
The lnner conductor or “hot” lead of
:
the cable should be connected to the
grld of the
hlgher values are
supplled with a 7-foot length
Longer cable lengths provlded wlth ml-
the table below. There
db below 1 volt per bar.)
tube
to 5 megohms. Al-
approximately
deslred. The shleld or
by a decrease
Output Level* at
Cable
speech
53.0 db
55.5 db
58.0 db
60.0 db
60.5 db
the
See
out-
no
-
output levels shown
does not have the necessary
ded
II cables are to be joined, the lnner leads should be
soldered and lnsulated with a good grade of rubber
tape.
should be soldered between the shields of the cable
to complete the shielding. Longer lengths
cost,
cables.
OPERATION:
accldently connected to loud speaker or power supply
outlets carrying hlgh voltage. Check your connections
carefully.
guarantee is volded by tampering with the mechanism.
places where the temperature exceeds
should not be exposed to the rays of the sun
hot weather for any
left
hot weather, as the temperature inside the
may easily bulld up to over
damage the crystal.
mum length of cable consistent wlth
cable shleld
(over)
Model 730S "Uniplex" Cardioid
Crystal Microphone
Most modern hlgh-gain
the
table.
or near the main ampllfler
the maln
Cable should be of hlgh quality
Metal brald sleeve or a serve of fine wire
standard plug attached may be purchased at small
may be used interchangeably with shorter
(See Catalog3
Crystal microphones may be seriously damaged
The microphone case should not be opened. Our
closed automoblles parked
used near a radlo transmitter, the
should be used. Careful grounding of the
low impedance output are
or
No polarlzlng voltage
crystal
advlsable.
system has low impedance
input.
should not be used or kept
have a
the
length of time
the sun
and permanently
at the
suggested.
capacity.
cables
required for
F. They
U.S.A.
very
or
Page 2
NO.
138
DATA SHEET
No special precautions beyond ordinary
care are necessary in the operation of the "Uniplex" microphones. They will operate efficiently
and dependably under all ordinary conditions.
ACOUSTIC
CONSIDERATIONS:
The high-frequency response of
the 730S is accentuated and
the low frequencies are attenuated to give a smoothly rising response
characteristic. (See Fig. C). The result of
this is a microphone in which a high degree of
speech intelligibility is achieved without undue loss of quality. The expression "cardioid
type" response simply means that the horizontal
polar characteristic approximates a cardioid of
ing the dead side (rear) of the microphone
towards the audience or other source of interfering sound, pickup can be concentrated on the
desired source. Reverberation energy pickup is
decreased approximately two-thirds. The microphone can be placed close to reflecting surfaces without objectionable effects if the rear
side of the microphone is toward the reflecting
surface. This is particularly valuable in small
halls.
It is desirable to experiment with microphone placement and orientation in order to
secure the greatest benefits from the unidirectional characteristic.
revolution. There is a wide, useful pickup
angle at the front of the microphone while the
response at the sides is down 6 db and the rear
response is down of the order of 15 db from the
front side response over a broad range of frequencies. The true unidirectional characteristic of the "Uniplex" should not be confused
Voltage Sensitivity: 2.25 millivolts r.m.s. per bar at
with the relatively slight directional effect
at high frequencies only which can be produced
by baffle-effects in the conventional pressure
microphone.
The result of this unidirectional characteristic is a complete elimination of acoustic
feedback at volume levels which would cause
This is equivalent to 53 db below 1 volt per bar.
Internal Output
Recommended Load
Impedance :
Impedance:
considerable feedback with conventional semidirectional microphones. In practically all
cases it is possible to increase loud-speaker
levels when a Uniplex is installed. By direct-
SPECIFICATIONS
the end of a 7-foot cable across
1 to 5 megohms at 400 cycles.
Equivalent to a 1500 micro-microfared condenser.
1 to 5 megohms.
Height, Overall (a)*. . . .
Height, Case (h)* . . . . . 3-1/8
Width (b)*. . . . . . . . . 3-1/8
Thickness (c)*. . . . . . .
Finish. . . . . . . . . . . Satin Chrome
Net Weight. . . . . . . . . 2-1/4 lbs.
Shipping Weight . . . . . . 2-1/2 lbs.
Code Word . . . . . . . . .
* See Fig. B.
GUARANTEE:
period of one year from date of shipment from
the factory, provided all instructions are
complied with fully. In case of damage, re-
turn the microphone to the factory for re-
pairs. Our guarantee is voided if the microphone case is opened.
LICENSE NOTICE:
FIG. C TYPICAL FREQUENCY RESPONSE. SHURE MODEL 730S "UNIPLEX" MICROPHONE
Each microphone is guaranteed
to be free from electrical
and mechanical defects for a
Shure patent 2,198,424. Other
patents allowed. Licensed
under patents of the Brush
Development Company.
4-3/8
3-3/8
RUPOD
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